This invention relates to the art of fluid filtration systems and, more particularly, to a self-cleaning system which is particularly applicable for reclaiming contaminated or dirty fluid, such as waste water in a vehicle washing system.
It is known in the art to provide fluid filtration systems for filtering fluid containing dirt, as in a vehicle washing system. Such filtration systems have included filtration tanks into which waste water is supplied and filtered by passing it through a filter bag. The filtered water is reclaimed for reuse in the vehicle washing system. It has been found that a filter bag having a filter rating on the order of 75 microns must be changed after washing approximately 500 vehicles. This results in considerable down time and, hence, expense to the operator of a vehicle washing system. It is desirable that such a vehicle washing system be provided with filters which are finer than 75 microns and preferably on the order of 50 or 25 microns and wherein several thousand vehicles may be washed before changing the filter or filters. Consequently, it would be advantageous to provide such a filter system which includes a self-cleaning filter.
A self-cleaning fluid filtration system is disclosed in the R. J. Shelstad U.S. Pat. No. 4,937,005. Shelstad's filtration system is intended to be used in a vehicle wash system or the like. The system includes a collapsible filter tube located in a tank into which dirty water is introduced by way of an inlet hose. The dirty water enters into the top of a chamber which coaxially surrounds the filter tube. The dirty water flows radially inward through the filter tube into the interior of the tube and then exits as filtered water from the interior of the tube by way of an outlet hose. The filter tube is movable between an uncollapsed filter position and a collapsed purge position. The movement of the filter tube is controlled by a timer which automatically determines when to actuate a cylinder and piston arrangement to drive the tube between the filter position and the purge position.
In Shelstad, the filter tube does not take the form of a typical filter bag, which is a replaceable item. Instead, the filter tube is provided at its lower end with a metal disk which is secured at its periphery to the filter tube and an upper disk which is secured at its periphery to the upper end of the filter tube. The filter tube may need to be replaced after a substantial number of washing cycles which may cause tearing and deterioration of filter tube. It is difficult to disassemble the filter tube from the disks and then repair and/or replace the filter tube.
The L. Durr U.S. Pat. No. 3,542,200 discloses a fluid filtering system employing a central perforated inlet conduit which permits water to flow upward through the conduit and then be directed radially outward through apertures in the conduit into a filter chamber which is surrounded by a lint bag located within a metal perforated basket. It is to be noted that the lint bag is easily removable but is not self-cleaning.